<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .login_user_name {
            color:#00f;
        }
    </style>
</head>
<body>
    <h2>js标识符</h2>
    <div class="login_user_name">张三</div>
</body>
<script>
    let num=1;
    let len=50;
    let num2=10;
    let $value=20;
    let aabb=10;
    // let return=10;
   // console.log($value)
  // let loginUserName='张三'
  // let LoginUserName='李四'
  //let login_user_name='王五'
 // let login-password-name='王五'



 
</script>
</html>